diff --git a/Data/SimpleIndex.hs b/Data/SimpleIndex.hs
--- a/Data/SimpleIndex.hs
+++ b/Data/SimpleIndex.hs
@@ -299,8 +299,8 @@
 ixUpdate :: (Eq k, Eq i2, Eq i3, Eq i4, Eq i5, Eq i6, Hashable k,
       Hashable i2, Hashable i3, Hashable i4, Hashable i5, Hashable i6) =>
            Indexed a k i2 i3 i4 i5 i6
-                -> k -> (a -> a) -> Maybe (Int, a, a, Indexed a k i2 i3 i4 i5 i6)
-ixUpdate ux uid f = 
+                -> k -> (a -> a) -> Maybe (Indexed a k i2 i3 i4 i5 i6)
+ixUpdate ux uid f = (\(_,_,_,f) -> f) `fmap`
     case ux of
         (IxHas1 b h1 f1) -> _ixUpdateData1 ux IxHas1 b h1 f1 uid f
         (IxHas2 b h1 f1 h2 f2) -> 
diff --git a/simple-index.cabal b/simple-index.cabal
--- a/simple-index.cabal
+++ b/simple-index.cabal
@@ -1,5 +1,5 @@
 name:                simple-index
-version:             0.1.0.0
+version:             0.1.0.1
 synopsis:            Allows simple indexation on any data type
 -- description:         
 license:             BSD3